Thermal power generating unit, flywheel and compressed air hybrid energy storage system and operation method thereof

Abstract

The invention discloses a thermal power generating unit, flywheel and compressed air hybrid energy storage system and an operation method, and relates to the technical field of flexibility improvement of novel energy storage and thermal power systems. The system comprises a flywheel energy storage subsystem, a compressed air energy storage subsystem, a thermal power collaborative heat exchange system, a flywheel-CAES switching coupling module and an intelligent control system. The flywheel energy storage subsystem is responsible for millisecond-level frequency modulation response, the compressed air energy storage subsystem provides minute-level stable output, and the flywheel energy storage subsystem and the compressed air energy storage subsystem cooperatively work through an intelligent control system to realize a composite regulation mode of'fast response-high capacity '; a compressed air side is coupled with a thermal power plant turbine steam extraction system, a boiler flue gas system and a condensed water system to improve the energy release efficiency; the flywheel side interacts with a power grid in real time through a bidirectional converter, and rapid frequency support is achieved. The system has the quick response capability and the long-time energy supporting capability, the frequency modulation and peak regulation performance of the thermal power generating unit is remarkably improved, and the system has high engineering popularization value and application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage and power system operation optimization, and in particular to a hybrid energy storage system of a thermal power unit, a flywheel and compressed air, and a combined frequency and peak regulation operation method thereof, belonging to the interdisciplinary research direction of new physical energy storage and flexible coordinated control applications of thermal power. Background Art

[0002] In my country's current power system, thermal power units still bear the primary responsibility for frequency and peak regulation. However, traditional thermal power units suffer from slow response speeds, low regulation accuracy, and frequent starts and stops. Long-term operation far from rated operating conditions leads to reduced fuel efficiency, increased equipment wear, and shortened unit lifespan.

[0003] To enhance the grid's regulation capabilities and alleviate the burden on thermal power generation units, energy storage systems are being widely researched and applied. Compressed air energy storage (CAES), a typical large-scale physical energy storage technology, can store energy during low-power periods and release it during peak load periods to participate in grid peak regulation. It boasts advantages such as large storage capacity, high system efficiency, and long lifespan. Flywheel energy storage systems, characterized by high power density and millisecond-level response speeds, are suitable for short-term frequency stabilization and rapid power regulation.

[0004] However, existing technologies often deploy both independently, failing to form a seamlessly integrated system. A single CAES system is slow to respond and cannot meet the grid's demand for rapid frequency support; flywheel systems, however, are limited in capacity and are only suitable for short-term use. Existing technologies lack a comprehensive solution that combines flywheel energy storage with CAES systems and deeply couples them with thermal power plants to achieve multi-time-domain coordinated regulation and frequency and peak regulation. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a thermal power unit, flywheel and compressed air hybrid energy storage system and its joint frequency regulation and peak regulation operation method, aiming to achieve the integrated regulation of millisecond-level frequency regulation response and long-term peak regulation support.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A thermal power unit, flywheel and compressed air hybrid energy storage system, comprising a flywheel energy storage subsystem, a compressed air energy storage subsystem, a thermal power coordinated heat exchange system, a flywheel-CAES switching coupling module 13 and an intelligent control system 14;

[0008] The flywheel energy storage subsystem includes a flywheel device 1, a magnetic bearing 2, a motor control module 3 and a bidirectional converter 4 connected in sequence, which are used to achieve rapid bidirectional conversion between electrical energy and kinetic energy;

[0009] The compressed air energy storage subsystem includes a multi-stage compressor 5, an intercooler 6, an air storage tank 7, an air expander 8 and an intermediate heat exchanger 9, which are used to complete the compression, storage, release and expansion power generation processes;

[0010] The thermal power coordinated heat exchange system includes a steam extraction interface 10, a flue gas heat exchanger 11 and a condensate heat exchanger 12, which are respectively coupled with the thermal power plant steam turbine, boiler tail and condensate system for heat energy replenishment and waste heat recovery;

[0011] The flywheel-CAES switching coupling module 13 connects the bidirectional converter 4 and the air expander 8 and is used for fast switching or parallel operation between the flywheel output and the compressed air energy release;

[0012] Intelligent control system 14, used to control compression energy storage, energy release power generation, power regulation, and heat flow path scheduling of the thermal power collaborative heat exchange system;

[0013] The various devices in the system are connected by cables or pipelines to form a composite energy storage operation network, which has the capabilities of rapid frequency regulation, long-term peak regulation and thermal coordination.

[0014] The flywheel device 1 is a high-speed rotating flywheel made of carbon fiber composite material with a rotation speed range of 10,000 to 25,000 rpm. The magnetic bearing 2 is used to support contactless rotation, and the motor control module 3 realizes energy charge and discharge conversion by adjusting the frequency conversion signal.

[0015] The multi-stage compressor 5 is a multi-stage piston compression structure, the intercooler 6 is a circulating water cooling heat exchanger, and the outlet temperature is controlled below 45°C; the air expander 8 adopts a double-cylinder isentropic structure, and the maximum output power is not less than 15MW.

[0016] In the thermal power coordinated heat exchange system, the steam extraction interface 10 is connected between the intermediate pressure section of the steam turbine and the reheater, the flue gas heat exchanger 11 is located in the front section of the boiler economizer, and the condensate heat exchanger 12 is arranged in front of the condensate pump inlet for auxiliary heating and waste heat recovery.

[0017] The flywheel-CAES switching coupling module 13 includes a high-voltage circuit breaker and an automatic switching busbar, and has a bidirectional electronic control function to achieve independent operation or parallel response between the flywheel and the air expander, with a switching time of no more than 20ms.

[0018] The intelligent control system 14 is equipped with an AGC interface and a scheduling algorithm module, which automatically determines the operating mode according to the amplitude and duration of the grid frequency deviation. Short-term fluctuations are responded to by the flywheel energy storage subsystem, and continuous fluctuations are output by the compressed air energy storage subsystem. The flywheel energy storage subsystem and the compressed air energy storage subsystem can work together to support high-intensity load changes.

[0019] The intelligent control system 14 has a heat source scheduling function. According to the heat storage status and thermal power operation conditions, it dynamically adjusts the valve opening of the steam extraction interface 10 and the flue gas heat exchanger 11, and gives priority to selecting high-quality heat sources for heating the air inlet of the air expander.

[0020] The system is suitable for coordinated operation of thermal power units of 300MW and above. The response time of the flywheel subsystem is no more than 100ms, and the comprehensive efficiency of the hybrid system is no less than 65%. It has the capabilities of rapid response, continuous energy supply and comprehensive utilization of waste heat.

[0021] The operating method of the system of the present invention is as follows:

[0022] During periods of low grid load, the intelligent control system 14 activates the compressor 5 to perform multi-stage compression on the ambient air. During the compression process, heat is partially removed by the intercooler 6 and directed to the flue gas heat exchanger 11 to preheat the heat storage medium.

[0023] The compressed air enters the gas storage tank 7 through the pipeline for high-pressure storage. The design pressure of the gas storage tank 7 is 1020MPa, and the volume is adjustable according to the level of the thermal power plant unit, usually 3000060000Nm 3 Meanwhile, the flywheel device 1, supported by magnetic bearings 2, stores energy through high-speed rotation. The flywheel speed can reach 10,000 to 30,000 rpm. The charging process is completed by the motor control module 3, and the power direction is controlled by the bidirectional converter 4.

[0024] During this stage, the intelligent control system 14 monitors the gas storage pressure, flywheel speed and heat source parameters in real time, and dynamically adjusts the power distribution between the compressor 5 and the flywheel to achieve optimal energy storage efficiency.

[0025] When the grid frequency drops or a power generation dispatch instruction is received, the system immediately switches to a power release state. The flywheel device 1 is switched to a power generation state by the motor control module 3, outputting power to the grid via the bidirectional converter 4, achieving millisecond-level frequency modulation response. Simultaneously, the air storage tank 7 releases high-pressure air, which first enters the steam extraction interface 10 for heat exchange with the waste heat from the turbine's intermediate-pressure section, then enters the flue gas heat exchanger 11 to absorb heat from the boiler exhaust gas, further increasing its temperature. The heated air flows into the air expander 8, where it expands and generates work, driving the independent power generation module and supplying power to the grid. The expanded air is then discharged into the intermediate heat exchanger 9, where it is coupled to the condensate heat exchanger 12 to recover waste heat from the exhaust gas and assist in preheating the boiler feed water. The intelligent control system 14 automatically determines the regulation mode based on the AGC instruction, rapidly responding to and optimizing resource scheduling.

[0026] Under the condition of continuous load fluctuation: the intelligent control system 14 activates the flywheel-CAES switching coupling module 13, connecting the flywheel device 1 in parallel with the output path of the air expander 8, thus achieving the transition from the "short-term high-frequency regulation" mode to the "medium- to long-term stable support" mode;

[0027] At the same time, the intelligent control system 14 dynamically adjusts the valve opening and heat distribution of the steam extraction interface 10 and the flue gas heat exchanger 11 according to the operating status of the thermal power plant; the intelligent control system 14 has adaptive redundant switching capabilities to ensure continuous response and stable output under high-frequency power fluctuations.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The present invention combines two typical physical energy storage technologies, giving full play to the technical advantages of each. Flywheel energy storage has the characteristics of high power density, fast response speed, and long cycle life. It can respond to grid frequency fluctuations at the millisecond level and undertake the regulation tasks of short-term frequency modulation and instantaneous load changes; compressed air energy storage (CAES) is suitable for medium- and long-term energy support. It has the advantages of large energy storage capacity and low unit cost, and can continuously and stably output power for tens of minutes to several hours. After coupling the two, a composite energy storage system with complementary time scales and multi-level energy output is formed, which greatly improves the overall flexibility and adaptability of the energy storage system.

[0030] This system is deeply coupled with thermal power units. By introducing waste heat resources such as turbine extraction steam, boiler exhaust, and condensate into the compressed air energy release path, it not only increases the inlet temperature of the compressed air during expansion, significantly improving expansion output efficiency, but also fully utilizes the thermal power plant's waste heat, improving the unit's operating economy. Furthermore, the system features a reverse assist function, preheating the boiler's inlet water through the exhaust gas heat exchanger, thereby reducing the boiler's initial fuel load and improving overall thermal efficiency.

[0031] The flywheel-CAES system features a highly intelligent control strategy. It dynamically selects an operating path based on the grid's frequency modulation signal. When frequency fluctuations are small, the flywheel energy storage subsystem responds quickly. When frequency deviations persist for longer periods, the system automatically switches to the CAES system's long-term regulation path. When necessary, the two systems are connected in parallel, enabling a smooth transition from millisecond-level response to minute-level energy supply. This effectively addresses the single-time response issue of existing energy storage systems and comprehensively improves the safety and stability of the grid.

[0032] Finally, the system's modular structure facilitates scalability and engineering implementation, making it suitable for thermal power plants of varying sizes and grid environments. The system can flexibly configure the number of flywheel energy storage subsystems, gas storage volume, and heat exchange scale based on frequency regulation capacity requirements. This system has promising prospects for technical dissemination and engineering application, and is expected to be widely deployed as a key supporting technology in new power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a schematic diagram of the overall structure of a thermal power unit, a flywheel and a compressed air mixed energy storage system according to the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] A thermal power unit, flywheel and compressed air hybrid energy storage system, comprising a flywheel energy storage subsystem, a compressed air energy storage subsystem, a thermal power coordinated heat exchange system, a flywheel-CAES switching coupling module 13 and an intelligent control system 14;

[0036] The flywheel energy storage subsystem includes a flywheel device 1, a magnetic bearing 2, a motor control module 3 and a bidirectional converter 4 connected in sequence, which are used to achieve rapid bidirectional conversion between electrical energy and kinetic energy;

[0037] The compressed air energy storage subsystem includes a multi-stage compressor 5, an intermediate cooler 6, an air storage tank 7, an air expander 8 and an intermediate heat exchanger 9, which are used to complete the compression, air storage, air release and expansion power generation processes; among them, when storing energy, an intermediate cooler 6 is set between the compressor 5 stages, and the compressed air compressed by the last-stage compressor 5 is cooled by the last-stage intermediate cooler 6 and then stored in the air storage tank 7; when releasing energy, the compressed air discharged from the air storage tank 7 first enters the intermediate heat exchanger 9 for heating and then enters the air expander 8 to perform work. The intermediate heat exchanger 9 is set between the stages of the air expander 8 to increase the temperature of the compressed air, and the exhaust gas of the last-stage air expander 8 directly enters the atmosphere.

[0038] The thermal power coordinated heat exchange system includes a steam extraction interface 10, a flue gas heat exchanger 11 and a condensate heat exchanger 12, which are respectively coupled with the steam turbine, the boiler tail and the condensate system of the thermal power plant for heat energy supply and waste heat recovery; wherein, the steam extraction interface 10 is connected between the intermediate pressure section and the reheater of the steam turbine, the flue gas heat exchanger 11 is located in the front section of the boiler economizer, and the condensate heat exchanger 12 is arranged in front of the condensate pump inlet.

[0039] The flywheel-CAES switching coupling module 13 connects the bidirectional converter 4 and the air expander 8 and is used for fast switching or parallel operation between the flywheel output and the compressed air energy release;

[0040] Intelligent control system 14, used to control compression energy storage, energy release power generation, power regulation, and heat flow path scheduling of the thermal power collaborative heat exchange system;

[0041] The intermediate heat exchanger 9 of the compressed air energy storage subsystem is connected to the condensate heat exchanger 12 of the thermal power co-exchange system to improve the inlet parameters of the air expander 8. The flywheel energy storage subsystem and the compressed air energy storage subsystem are simultaneously connected to the flywheel-CAES switching coupling module 13. Specifically, the bidirectional converter 4 of the flywheel energy storage subsystem and the air expander 8 of the compressed air energy storage subsystem are respectively connected to the flywheel-CAES switching coupling module 13, which is then connected to the intelligent control system 14 via electrical wires. The thermal power plant DCS of the thermal power co-exchange system is directly connected to the intelligent control system 14, which coordinates the energy storage and output of the flywheel energy storage subsystem, the compressed air energy storage subsystem, and the thermal power co-exchange system.

[0042] The various devices in the system are connected by cables or pipelines to form a composite energy storage operation network, which has the capabilities of rapid frequency regulation, long-term peak regulation and thermal coordination. Specific embodiments

[0044] At a 300MW subcritical coal-fired power plant site, the system of the present invention is deployed as a frequency and peak regulation auxiliary module for the unit. The system components are configured as follows:

[0045] Flywheel device 1: uses a high-speed carbon fiber composite flywheel with a speed range of 10,000 to 25,000 rpm, a single energy storage capacity of 2 MJ, and is arranged in 4 groups in a string with a total capacity of 8 MJ. It operates in conjunction with magnetic bearing 2;

[0046] Motor control module 3: has bidirectional frequency conversion and regulation functions, with a maximum motor power of 5MW; bidirectional converter 4: uses a three-level IGBT module, supports millisecond-level current switching, and stably supports ±3MW dynamic power regulation;

[0047] Compressor 5: three-stage piston compression structure, compression ratio 14, motor rated power 12MW; Intercooler 6: shell and tube heat exchanger, using circulating water cooling, outlet temperature controlled below 45°C; Gas storage tank 7: designed capacity 45000Nm 3 , working pressure 16MPa, equipped with high pressure safety valve;

[0048] Air expander 8: adopts a double-cylinder isentropic expansion structure, imported thermal insulation layer and multi-point lubrication system, with a maximum power generation capacity of 15MW; intermediate heat exchanger 9: connected to the condensate heat exchanger 12, with a heat exchange area of ​​220m 2 , the outlet temperature is controlled below 90℃; extraction steam interface 10: arranged between the intermediate pressure cylinder of the steam turbine and the reheater, with an extraction steam flow rate of 5-10t / h; flue gas heat exchanger 11: installed in the front section of the economizer at the tail of the boiler, with a heat capacity of about 30MW;

[0049] Condensate heat exchanger 12: Located before the condensate pump inlet, it assists in preheating and recovering exhaust heat; Flywheel-CAES switching coupling module 13: An electrically switched busbar interface module equipped with an electronic switch, with a switching delay of no more than 20ms;

[0050] Intelligent control system 14: It is arranged in the power plant's centralized control room and is interconnected with the power plant's DCS using industrial Ethernet. It includes an AGC data interface and a dispatching module.

[0051] The system operation process is as follows:

[0052] During the daytime peak load period, the grid dispatcher issues an AGC command. Flywheel device 1 first responds to frequency fluctuations, releasing kinetic energy to output instantaneous power. Intelligent control system 14 determines that the frequency fluctuation has lasted for more than 5 seconds and immediately activates the compressed air path. Air storage tank 7 opens the electronically controlled valve, and high-pressure air is heated by steam extraction interface 10 and flue gas heat exchanger 11 before entering air expander 8 to expand and perform work.

[0053] The expanded tail gas enters the intermediate heat exchanger 9 and is coupled with the condensate heat exchanger 12 to improve the heat recovery efficiency and realize the output of low-temperature hot water.

[0054] The intelligent control system 14 dynamically adjusts the flywheel output ratio and the gas storage energy release rate according to load changes to achieve a smooth transition of the power curve and continuous frequency modulation support.

[0055] Actual measurements show that in terms of frequency modulation response time, the first response time of the system of the present invention is less than 100ms; the output is stable under a 10-minute continuous peak regulation scenario, and the total system efficiency reaches more than 65%; the heat source utilization rate is increased by about 20%.

Claims

1. A thermal power unit, flywheel and compressed air hybrid energy storage system, characterized in that: It includes a flywheel energy storage subsystem, a compressed air energy storage subsystem, a thermal power coordinated heat exchange system, a flywheel-CAES switching coupling module (13) and an intelligent control system (14); The flywheel energy storage subsystem comprises a flywheel device (1), a magnetic suspension bearing (2), a motor control module (3) and a bidirectional converter (4) connected in sequence, and is used to realize rapid bidirectional conversion between electrical energy and kinetic energy; The compressed air energy storage subsystem includes a multi-stage compressor (5), an intermediate cooler (6), an air storage tank (7), an air expander (8) and an intermediate heat exchanger (9), and is used to complete the compression, air storage, air release and expansion power generation processes; The thermal power coordinated heat exchange system includes a steam extraction interface (10), a flue gas heat exchanger (11) and a condensate heat exchanger (12), which are respectively coupled with the steam turbine, the boiler tail and the condensate system of the thermal power plant for heat energy replenishment and waste heat recovery; A flywheel-CAES switching coupling module (13) is connected to the bidirectional converter (4) and the air expander (8) and is used for fast switching or parallel operation between flywheel output and compressed air energy release; An intelligent control system (14) for controlling compression energy storage, energy release power generation, power regulation, and heat flow path scheduling of a heat exchange system coordinated with a thermal power plant; Among them, the intermediate heat exchanger (9) of the compressed air energy storage subsystem is connected to the condensate heat exchanger (12) of the thermal power coordinated heat exchange system to improve the inlet parameters of the air expander (8); the flywheel energy storage subsystem and the compressed air energy storage subsystem are simultaneously connected to the flywheel-CAES switching coupling module (13), specifically, the bidirectional converter (4) of the flywheel energy storage subsystem and the air expander (8) of the compressed air energy storage subsystem are respectively connected to the flywheel-CAES switching coupling module (13), and the flywheel-CAES switching coupling module (13) is connected to the intelligent control system (14) by wires; the thermal power plant DCS of the thermal power coordinated heat exchange system is directly connected to the intelligent control system (14), and the intelligent control system (14) uniformly coordinates and allocates the energy storage and output of the flywheel energy storage subsystem, the compressed air energy storage subsystem and the thermal power coordinated heat exchange system.

2. The system according to claim 1, wherein: The flywheel device (1) is a high-speed rotating flywheel made of carbon fiber composite material with a rotation speed range of 10,000 to 25,000 rpm. The magnetic suspension bearing (2) is used to support contactless rotation. The motor control module (3) realizes energy charge and discharge conversion by adjusting the variable frequency signal.

3. The system according to claim 1, wherein: The multi-stage compressor (5) is a multi-stage piston compression structure, the intercooler (6) is a circulating water cooling heat exchanger, and the outlet temperature is controlled below 45° C.; the air expander (8) adopts a double-cylinder isentropic structure, and the maximum output power is not less than 15MW.

4. The system according to claim 1, characterized in that In the thermal power coordinated heat exchange system, the extraction steam interface (10) is connected between the intermediate pressure section and the reheater of the steam turbine, the flue gas heat exchanger (11) is located in the front section of the boiler economizer, and the condensate heat exchanger (12) is arranged in front of the condensate pump inlet for auxiliary heating and waste heat recovery.

5. The system according to claim 1, wherein: The flywheel-CAES switching coupling module (13) includes a high-voltage circuit breaker and an automatic switching busbar, and has a bidirectional electronic control function to realize independent operation or parallel response between the flywheel and the air expander, with a switching time of no more than 20ms.

6. The system according to claim 1, wherein: The intelligent control system (14) is equipped with an AGC interface and a dispatching module, and automatically determines the operation mode according to the amplitude and duration of the grid frequency deviation. Short-term fluctuations are responded to by the flywheel energy storage subsystem, and continuous fluctuations are output by the compressed air energy storage subsystem. The flywheel energy storage subsystem and the compressed air energy storage subsystem work together to support high-intensity load changes.

7. The system according to claim 1, wherein: The intelligent control system (14) has a heat source scheduling function. According to the heat storage state and the thermal power operation conditions, it dynamically adjusts the valve opening of the steam extraction interface (10) and the flue gas heat exchanger (11), and gives priority to selecting a high-quality heat source for heating the air inlet of the air expander.

8. The system according to claim 1, wherein: The response time of the flywheel energy storage subsystem is no more than 100ms, and the comprehensive efficiency of the hybrid energy storage system is no less than 65%. It has the ability of rapid response, continuous energy supply and comprehensive utilization of waste heat.

9. The method for operating the system according to any one of claims 1 to 8, characterized in that: During periods of low grid load, the intelligent control system 14 activates the compressor 5, performing multi-stage compression on the ambient air. During the compression process, heat is partially removed by the intercooler 6 and directed to the flue gas heat exchanger 11 to preheat the heat storage medium. The compressed air then enters the gas storage tank 7 via a pipeline for high-pressure storage. Simultaneously, the flywheel device 1, supported by the magnetic bearing 2, rotates at high speed to store energy. During this phase, the intelligent control system 14 monitors the gas storage pressure, flywheel speed, and heat source parameters in real time, dynamically adjusting the power distribution between the compressor 5 and the flywheel to achieve optimal energy storage efficiency. When receiving a grid frequency drop or a dispatch power generation instruction, the system immediately switches to the energy release state; the flywheel device 1 is switched to the power generation state by the motor control module 3, and outputs power to the grid through the bidirectional converter 4, achieving millisecond-level frequency modulation response; at the same time, the air storage tank 7 releases high-pressure air, which first enters the steam extraction interface 10 for heat exchange with the waste heat of the medium-pressure section of the steam turbine, and then enters the flue gas heat exchanger 11 to absorb the heat of the boiler exhaust gas for further temperature increase; the heated air flows into the air expander 8 to expand and perform work, driving the independent power generation module and supplying power to the grid; the expanded air is discharged into the intermediate heat exchanger 9 and coupled with the condensate heat exchanger 12 to realize exhaust gas waste heat recovery and assist in boiler feed water preheating; the intelligent control system 14 automatically determines the adjustment mode according to the AGC instruction, quickly responds and optimizes resource scheduling; Under the working condition of continuous load fluctuation: the intelligent control system 14 activates the flywheel-CAES switching coupling module 13, connects the flywheel device 1 in parallel with the output path of the air expander 8, and realizes the transition from short-term high-frequency regulation to medium- and long-term stable support mode; At the same time, the intelligent control system 14 dynamically adjusts the valve opening and heat distribution of the steam extraction interface 10 and the flue gas heat exchanger 11 according to the operating status of the thermal power plant; the intelligent control system 14 has adaptive redundant switching capabilities to ensure continuous response and stable output under high-frequency power fluctuations.

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